Answer:- b. +3
Explanations:- Charge of a metal ion is equal to the number of valence electrons it has as it loses these electrons to have its nearest noble gas like electron configuration.
Al has 3 valence electrons and being a metal it loses all of these and so the charge of Al ion is +3. It could be shown as:
[tex]Al\rightarrow Al^+^3+3e^-[/tex]
So, the right choice is b. 3+.
